The vigor of birdsfoot trefoil seedlings has been increased by selection. Because they, like the unimproved type, are susceptible to root rots, however, it has been difficult to establish good stands in warm climates. Selection for reduced shattering and for a prostrate plant type has been partly successful.

A yellow lupine with nonshattering pods has been found, but this character is still lacking in commercial lupines for forage. Some lupine selections made in Georgia bear certain genetic markers that would permit the identification of a variety and a determination of its purity in the field. Such markers are greatly needed in many forage crops in order that the purity of improved strains can be maintained.

IMPROVED VEGETABLE seeds include Ferry's Round Dutch cabbage and Great Lakes lettuce. They are outstanding products of selection for resistance to bolting. Ferry's Round Dutch was selected to permit heading and eliminate bolting after periods of cold weather. Great Lakes was selected to permit heading during periods of warm weather, when most varieties of head lettuce bolt.

Genetic safeguards against loss from premature bolting are essential. It is possible to breed strains that will bolt and flower only under unusual conditions. Often, therefore, they produce no seed. An individual cabbage plant selection may or may not flower after the usual cold treatment of 2 months at 37 F.

The yield of commercial seed of Great Lakes and other slow-bolting varieties of lettuce was low until better seed-producing selections were developed.

CERTAIN CHARACTERS, such as non-shattering of seed, appear to have been developed during domestication because the wild forms of many crops drop their seeds as soon as they are ripe. Non-shattering of garden lettuce is of utmost importance in the commercial production of seed. The wild Lactuca serriola, which depends for its existence on shattering of the seed, differs in this respect from garden lettuce by only a single dominant gene.

Most breeding of vegetables is concerned with the yield and the eating, preserving, and shipping qualities of the part of the plant that is consumed. Seed fields may contain individuals having such characters as heavy growth, numerous flowers, or large fruits, which favor high yields of seed. Selection for high yield of seed must avoid any concurrent selection of undesirable market types. The two breeding objectives must therefore be coordinated.

The areas producing vegetables for market and for seed often are widely separated, with different growing conditions, a fact that tends to complicate the breeding and maintenance of seed stock.

In melons, squash, and pumpkin, in which the fruit is eaten but the seeds discarded, the consumer may wrongly think that large seed is an indication of coarse texture of the flesh. Large seeds may also detract from the appearance of cut watermelon fruit. In general, seeds of medium size are preferred. Many think that a black seed gives a pleasing contrast to the red flesh of the watermelon, although a dark-brown seed also is considered acceptable. A dark seed may also be used as an indication of a desirable stage of maturity.

Seeds of tomatoes, cucumbers, egg-plants, and peppers are eaten incidentally. They must be unobtrusive. A tough seedcoat may be objectionable in the slicing cucumber and in "seedless" watermelons. In the latter, the seeds abort because the plants are sterile triploids, the result of crossing normal diploid watermelons with special tetraploid strains that have the double number of chromosomes. The best seedless varieties produced thus far have been developed by doubling the chromosome complement of small-seeded, small-fruited varieties. The undeveloped coats of the aborted seeds are inconspicuous and are eaten with the melon flesh. Work on large-fruited varieties is in progress.

IN CROPS grown for their seed, the size and shape of the seed must conform to accepted standards. The seed varieties of lima bean may differ in size and shape, such as the large, thick seeds (potato type) and medium to small thin seeds (sievas). The latter is simple dominant to the former type. Differences in seed size among the thin sieva limas may result from complementary action of nonallelic genes.

Shape of seed is important in sweet corn. A relatively narrow, deep kernel is preferred for both fresh consumption and canning. Sweetness and tenderness are even more important.

COLOR OF seed is important. Most commercial requirements are met by using only few of the rich assortment of colors and patterns that are available among the breeding stocks in the world.

In beans, the colors are in the seed-coat. Colored seed generally has given better germination and vigor than white seed, which canners prefer. Small amounts of color develop in the seed of colored sorts at a very early stage. Some of the color is released during processing, and the liquid gets a murky appearance. Because a clear liquid is preferred, much work has gone into the breeding of white-seeded varieties that germinate as well as those with colored seed.

Most sweet corn is yellow or white. The yellow color results from xanthophyll, cryptoxanthin, and carotene in the endosperm. The carotene gives added nutritive value compared with white corn. The yellow color varies, depending on the genes present, from pale yellow to deep orange. The color usually deepens for each gradation as the kernels mature. Most sweet corn hybrids are a light yellow, which avoids the appearance of over-maturity, although the deeper yellows supply larger amounts of carotene. Another vitamin, niacin, ranges from 18 to 62 micrograms per gram of air-dry kernel. Selection for higher niacin content should prove effective.